Continuous Flow Synthesis: A Short Perspective

Abstract

In the past few years, continuous flow processing has slowly started to find place in academic research. Considered more of an industrial value for large-scale synthesis in chemical industry, it took more than half a century for academia to slowly adopt this technology for small-scale laboratory synthesis. Although there are clear benefits, especially whenever working with hazardous intermediates, that have to be generated in situ, or rapid heat dissipation and efficient mixing are needed, the general use of continuous flow synthesis on a daily basis in the modern research laboratory remains controversial. Still, flow synthesis appears to be seen as a curiosity and merely an expert tool among the many other and more “traditional” synthesis techniques. As such, the plethora of recent examples found in the literature remains focused on exploring the capabilities of the available equipment for optimizing already established syntheses and rarely a novelty from a chemical point of view is found. The challenge of processing heterogeneous reactions and reagents, highly viscous or highly corrosives materials, as well as the required time and labor investment for developing a running flow process depict further hurdles. Nevertheless, and in many instances, the use of dedicated flow equipment has proven its value and can bring undisputable advantage for the synthetic chemist in the research laboratory—continuous flow hydrogenation, ozonolysis, or lithium exchange reactions are just some of these synthetic examples. Although continuous flow technology offers a technically unique way to perform synthetic reactions, the question of whether to use this technique for a chemical transformation should be taken by an experienced chemist.